A turbocharger or "turbo" is an air compressor used in a forced induction, internal combustion engine, that increases the density of the air going into the intake, allowing it to burn more efficiently.

A turbocharger works by a turbine driven by the engine's exhaust gas, which drives the compressor fan to force air into the engine.

An intercooler can be added in addition to this, allowing the air to be cooler, as air is denser at lower temperatures.

Unlike superchargers, which are driven by the torque of the engine, a turbocharger's power may take some time to gather the pressure required to turn the turbine fast enough to produce significant boost this is called the "lag" effect, and is more common with single larger turbochargers.

Passenger: "Oh man my head is in my stomach right now"

Driver: "That would be the huge rush of power produced by the turbocharger!"